In a radio communication apparatus such as a mobile terminal, one antenna is shared with transmission and reception, and a connection to the antenna is frequently switched over between the transmission and the reception by an antenna switch. Also, in the case where the mobile terminal is adaptive to plural communication systems, the antenna switch is so structured as to switch over the connections of the antenna between plural transmitting circuits and plural receiving circuits. It is general signal that is outputted from the transmitting circuits is large in electric power so as to exceed 1 W in a cellular phone. The antenna switch is set with such a performance that the transmitted signal large in the electric power is high in quality, and does not include an interfering wave that adversely affects the communication of another frequency band. Accordingly, in the case of using the switching element using a transistor as the antenna switch, the switching element is so designed as to be high in withstand voltage and suppress a harmonic distortion to a lower value.
In the case of using a field effect transistor for the switching element, there are generally conducted an improvement in the withstand power property by using a multi-gate transistor in which plural gates are disposed between two ohmic electrodes (a drain electrode and a source electrode), and a more improvement in the withstand power property by connecting the multi-gate transistors in multi-stages. Patent document 1: Japanese Patent Laid-open No. 2000-101032 discloses an example of a structure in which n+ electrodes that are formed between gate electrodes as inter-gate regions are connected to ohmic electrodes through resistors higher in resistance value than the n+ electrodes in the multi-gate transistor. An example of a structure having four gate electrodes is shown in FIG. 16. The gate electrodes 18 to 20 and the n+ electrodes 22 to 24 are disposed between the ohmic electrodes 16 and 17, and the n+ electrodes 22 to 24 are connected to the ohmic electrodes 16 and 17 through potential stabilization resistors 25 to 28.